Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 231819
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
219 PM EDT SAT AUG 23 2014

.SYNOPSIS...
A BACK DOOR COLD FRONT WILL PUSH INTO THE AREA FROM THE NORTHEAST
THIS EVENING AND TONIGHT...USHERING IN COOLER TEMPERATURES STARTING
SUNDAY. DRY AND COOLER CONDITIONS WILL CONTINUE THROUGH MID NEXT
WEEK AS A WEDGE OF SURFACE HIGH PERSISTS ACROSS THE REGION.

&&

.NEAR TERM /THROUGH SUNDAY/...
AS OF 200 PM EDT...DEEP LAYER NW FLOW PERSISTS THIS AFTN BETWEEN A
STRONG HIGH PRES RIDGE OVER THE CENTRAL CONUS AND LOW PRESSURE
OFFSHORE OF NEW ENGLAND. AN MCV SLIDING SWD EAST OF THE RIDGE IS
PASSING THROUGH ERN TN THIS AFTN AND MAY JUST BRUSH THE EXTREME SRN
APPALACHIANS THROUGH LATE AFTN. MOST OF THE FORCING THROUGH THE
EVENING HOURS SHOULD FOCUS ALONG THE APPROACHING BACKDOOR COLD FRONT
WHERE LOW LEVEL CONVERGENCE WILL BE STRONGEST. ALTHOUGH COVERAGE MAY
END UP BEING A BIT BETTER ALONG THE IMMEDIATE FRONTAL ZONE...850 TO
500 MB LAPSE RATES WILL BE GREATEST OVER THE UPPER SAVANNAH RIVER
REGION THIS EVENING...AND THAT IS WHERE CONVECTION MIGHT BECOME
STRONGEST. THE SFC FRONT WILL CONTINUE TO WORK THROUGH THE REGION
TONIGHT FROM NE TO SW OVERNIGHT. BEHIND THE BOUNDARY...EASTERLY
UPSLOPE FLOW SHOULD TRIGGER CONVECTION IN SW VA WHICH WILL THEN
LIKELY SLIDE SWD ALONG THE ERN ESCARPMENT OF THE MOUNTAINS OVERNIGHT
INTO SUNDAY MORNING. THAT IS WHERE THE GREATEST POTENTIAL FOR
LOCALLY HEAVY RAINFALL WILL BE...BUT HEAVY RAIN AND LOCALIZED HYDRO
PROBLEMS COULD DEVELOP IN ANY LOCATIONS EXPERIENCING TRAINING.
EXPECT VERY WARM MINS GIVEN THAT ALL THE THICKNESS FALLS ARE WELL NE
OF THE FRONT AND WILL TAKE UNTIL SUNDAY TO ARRIVE...AND LOW CLOUDS
WILL FILL IN BEHIND THE FRONT TO KEEP TEMPS WARM.

THE DEEP AND STRONG RIDGE AXIS STRETCHING FROM THE MOUTH OF THE MS
RIVER TO THE GREAT LAKES WILL THEN BUILD EWD TOWARD THE APPALACHIANS
THROUGH SUNDAY. AT THE SFC...HIGH PRES WILL STEADILY NOSE INTO THE
REGION AS THE FRONTAL BOUNDARY SETTLES JUST SW OF THE AREA. DEEP
MOIST EASTERLY FLOW WILL KEEP CONSIDERABLE CLOUDS ACROSS THE REGION
ON SUNDAY AND SPAWN AT LEAST SCATTERED SHOWER COVERAGE. WEAK
THUNDERSTORMS WILL BE POSSIBLE AS WELL NEAR THE ESCARPMENT AND IN
ELEVATED INSTABILITY IN SW SECTIONS. IN ADDITION...THE DEEPER
MOISTURE POOL WILL GET SHUNTED TOWARD SRN SECTIONS OF THE FORECAST
AREA BY LATE SUNDAY TO PUSH THE GREATER HEAVY RAINFALL THREAT THERE.
MAXES SHOULD RUN AT LEAST ONE TO TWO CATEGORIES BELOW CLIMO.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY/...
AS OF 245 AM SATURDAY...ON SUNDAY...THE WEDGE FRONT WILL REACH
ACROSS THE DEEP SOUTH BY SUNRISE. RIDGING HIGH PRESSURE WILL REMAIN
ACROSS THE FORECAST AREA ON SUNDAY. THE FORECAST WILL FEATURE
ABUNDANT CLOUD COVER AND STEADY ENE WINDS. POPS WILL REMAIN IN THE
CHC RANGE ACROSS THE MTNS AND NE GA...HIGHLIGHTING LINGERING WEAK
INSTABILITY AND UPSLOPE FLOW. ELSEWHERE...CONDITIONS SHOULD
GENERALLY REMAIN DRY. HIGH TEMPERATURES ARE FORECAST TO RANGE IN THE
70S ACROSS THE HIGH TERRAIN...LOW TO MID 80S ELSEWHERE.

MONDAY...SHORT RANGE MODELS SHOW DEEP DRY AIR ADVECTING SW ACROSS
THE FORECAST AREA. IN ADDITION...THE CENTER OF H5 RIDGE IS EXPECTED
LIFT NORTH ACROSS THE MID MISSISSIPPI RIVER VALLEY...WITH THE
EASTERN EDGE OF THE RIDGE ACROSS THE SOUTHERN APPALACHIANS. GFS
FORECAST SOUNDINGS APPEAR QUITE DRY...PW LESS THAN .75 AND WARM
TEMPERATURES ABOVE H8. SCHC POPS WILL BE LIMITED TO THE WESTERN NC
MTNS...NO MENTIONABLE POPS ACROSS THE REMAINDER OF THE CWA.
TEMPERATURES SHOULD RANGE CLOSELY TO SUNDAY/S VALUES.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
AS OF 3 AM SATURDAY...TUESDAY AND WEDNESDAY...SFC RIDGING WILL
CONTINUE ACROSS THE CWA...BUT TRENDING WEAKER WITH LIGHTER WINDS.
THE CENTER OF H5 590DM RIDGE WILL LIKELY SHIFT ACROSS THE SOUTHEAST.
TEMPERATURES SHOULD WARM TO NEAR NORMAL BY WEDNESDAY...AIDED BY
WARMING LLVL THICKNESSES AND INSOLATION. FORECAST SOUNDINGS INDICATE
THAT CONDITIONS WILL REMAIN DRY AND STABLE...SUPPORTING SINGLE DIGIT
POPS. THURSDAY AND FRIDAY...TROPICAL LOW IS EXPECTED TO TRACK OFF
THE CAROLINA COAST. THE GFS INDICATES THAT A COLD FRONT WILL SWEEP
ACROSS THE REGION ON FRIDAY...ACCOMPANIED BY A LONGWAVE TROF. THE
ECMWF KEEPS THE REGION UNDER MID LEVEL RIDGING AND SFC HIGH
PRESSURE...KEEPING ANY SFC BOUNDARIES WELL NORTH OF THE REGION.
NATIONAL GUIDANCE FAVORS THE ECMWF SOLUTION. I WILL INDICATE
SEASONABLE TEMPS WITH DIURNAL CHC POPS.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
AT KCLT...CONVECTIVE COVERAGE SHOULD FILL IN ALONG THE APPROACHING
BACK DOOR COLD FRONT THROUGH THE EVENING HOURS. THIS IS CURRENTLY
HANDLED WITH TEMPO TSRA 22Z TO 02Z...BUT NEARBY SHOWERS AND ISOLD
TSRA COULD BE AN ISSUE IN THE DEEP MOISTURE THROUGH MUCH OF THE
NIGHT. NE WINDS WILL PICK UP WITH FROPA AND A LOWER CLOUD DECK WILL
ARRIVE FROM THE NE BY 08Z. THE GUIDANCE IS SPLIT...BUT THERE IS A
TREND TOWARD IFR ON BOTH THE MAV AND MET WHILE THE LAMP REMAINS
MVFR. HAVE LOWERED THE MVFR CIGS FORECAST FOR THE OVERNIGHT
HOURS...BUT IFR REMAINS A POSSIBILITY. EXPECT ONLY SLOW RECOVERY
THROUGH MVFR SUNDAY MORNING WITH SHOWERS REMAINING IN THE
VICINITY...ALONG WITH PERSISTENT NE FLOW.

ELSEWHERE...CONVECTION IS FILLING IN MAINLY IN THE MOST UNSTABLE
AREAS OF THE SRN ESCARPMENT...AND STEERING FLOW MAY TAKE THESE CELLS
TOWARD THE UPSTATE TAF SITES THROUGH 20Z. A VCTS IS CURRENTLY
FEATURED...BUT A TEMPO TSRA COULD BE ADDED THERE IN THE NEAR FUTURE.
OTHERWISE...COVERAGE IS EXPECTED TO EXPAND ALONG THE APPROACHING
BACK DOOR COLD FRONT. THIS SHOULD YIELD THE BEST THUNDER CHANCES
THROUGHOUT DURING THE EVENING HOURS. EXPECT VFR CIGS THIS EVENING TO
GIVE WAY TO LOWER MVFR CIGS OVERNIGHT WITH FROPA FROM NE TO
SW...WITH IFR LIKELY AT KHKY BEFORE DAYBREAK. KHKY TO KAVL MAY SEE
THE BEST CHANCE OF CONTINUED SHOWERS IN EASTERLY UPSLOPE THROUGH
SUNDAY MORNING. CIGS WILL BE VERY SLOW TO RECOVER THROUGH SUNDAY
MORNING WITH THE PERSISTENT MOIST EASTERLY FLOW...WITH NOTHING
HIGHER THAN MVFR TO LOWER END VFR BY 18Z THROUGHOUT.

OUTLOOK...DRYING ON CONTINUED NE FLOW IS EXPECTED MONDAY THROUGH
TUESDAY. DIURNAL THUNDERSTORMS MAY RETURN TO THE MTNS MID WEEK.
MORNING LOW CLOUDS AND FOG WILL BE POSSIBLE...ESPECIALLY IN THE MTN
VALLEYS.

CONFIDENCE TABLE...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH 100%     HIGH  94%     HIGH  94%     HIGH  98%
KGSP       HIGH 100%     HIGH 100%     HIGH  87%     HIGH 100%
KAVL       HIGH 100%     HIGH  95%     HIGH  81%     HIGH  87%
KHKY       HIGH 100%     HIGH  90%     HIGH  84%     HIGH  89%
KGMU       HIGH 100%     HIGH 100%     HIGH  91%     HIGH  95%
KAND       HIGH 100%     HIGH 100%     HIGH  97%     HIGH  92%

THE PERCENTAGE REFLECTS THE NUMBER OF GUIDANCE MEMBERS AGREEING
WITH THE SCHEDULED TAF ISSUANCE FLIGHT RULE CATEGORY. COMPLETE
HOURLY EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE
FORECASTS ARE AVAILABLE AT THE FOLLOWING LINK: (MUST BE LOWER CASE)

WWW.WEATHER.GOV/GSP/AVIATION_TABLES

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.

&&

$$
SYNOPSIS...HG
NEAR TERM...HG
SHORT TERM...NED
LONG TERM...NED
AVIATION...HG





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